1. Field of the Invention
This invention relates to a glare tester and more specifically to a glare tester attachment suitable for use with a standard ophthalmic instrument.
2. Brief Description of the Prior Art
In recent years it has been discovered that the visual acuity of a patient measured in a standard dark refracting lane in an ophthalmologist""s or optometrist""s office may not be indicative of the patient""s acuity in conditions of bright light or glare, especially where the patient suffers from eye disorders such as cataracts or corneal scars. In order to provide a more thorough assessment of a patient""s visual acuity, brightness acuity or xe2x80x9cglarexe2x80x9d testers have been devised. One type of glare tester subjects the eye to be tested to a bright generally uniform illumination while the patient observes a test chart, e.g., a standard Snellen chart. This xe2x80x9cbrightness acuity testxe2x80x9d provides an objective measurement of visual acuity under bright light conditions. It is useful to evaluate visual problems caused by cataracts, corneal scarring, and other conditions that cause intraocular light scattering. Alternatively, the eye may be subjected to a macular photostress test to detect possible maculopathy. In the photostress test, the visual acuity of the eye is first determined under conventional testing conditions. The eye is then subjected to bright illumination for a certain length of time (xe2x80x9cphotostress conditionsxe2x80x9d). The eye""s acuity is retested under conventional conditions after one or more resting intervals to permit recovery of the retina. The period required for recovery of normal visual acuity is indicative of possible macular disturbances, e.g., cystoid macular edema or senile macular degeneration. A glare tester suitable for performing such tests is disclosed in, for example, U.S. Pat. No. 4,784,483 to Holladay et al., the entire disclosure of which is incorporated herein by reference.
Such a glare tester comprises an illumination source of predetermined intensity situated in an open-sided, generally concave illumination chamber sized to occlude the tested eye. The interior of the chamber is provided with a diffusively reflective wall, whereby the eye is subjected to a generally uniform illumination. A test chart may be viewed through an aperture in the chamber wall opposite the eye to perform a brightness acuity test. Alternatively, the viewing aperture may be occluded to provide a photostress to the eye for a predetermined period, after which the visual acuity is tested to evaluate the effect of the photostress on vision as described above.
A glare tester of this type typically comprises a handle containing a source of power, e.g., batteries, with the illumination chamber mounted at one end of the handle. In use, the illumination chamber is held in position in front of the eye to be tested by the patient or examining ophthalmologist. The patient then follows the instructions of the examiner in performing a brightness acuity test or a photostress test as described above.
Although such glare testers have made this form of acuity testing relatively convenient and have encouraged such testing, the currently available glare testers of this type have certain disadvantages. Current testers are marketed as separate instruments that require the use of a separate charging unit and are not capable of being recharged in a standard recharging well used for other examination instruments such as ophthalmoscopes, retinoscopes, and transilluminators. Furthermore, even if a separate glare tester were compatible with standard recharging units, such units typically do not provide enough charging wells to accommodate a glare tester in addition to the conventional ophthalmic examination instruments. Consequently, an entire separate instrument and recharger must be purchased in order to conduct glare testing.
Accordingly, a need has continued to exist for a simple and inexpensive glare testing apparatus, preferably usable with standard ophthalmic examination instruments.
The need has been alleviated by the present invention, which, according to its various aspects, provides a glare testing attachment that can be mounted on a conventional transilluminator or ophthalmoscope so as to use the light source provided in those instruments.
Accordingly, the glare tester of the invention incorporates
a generally concave reflector for providing diffuse illumination to an eye, the reflector comprising a wall having an interior light-reflecting surface partially enclosing a hollow interior chamber;
mounting means for removably supporting the reflector on a source of illumination; and
means for conducting illumination from the source of illumination to the interior light reflecting surface.
Accordingly, it is an object of the invention to provide an instrument for testing the effect of glare on visual acuity.
A further object is to provide a convenient and inexpensive glare tester.
A further object is to provide a glare tester that can be attached to a standard transilluminator.
A further object is to provide a glare tester that can be attached to a standard ophthalmoscope.
A further object is to provide a glare tester that can be recharged in a standard ophthalmic recharging well.
Further objects of the invention will be apparent from the description of the invention which follows.